Experimental method for determining starting pressure gradient of seepage

Abstract

The invention provides an experimental method for determining initiation pressure gradient of seepage, and belongs to the technical field of oil and gas field development and test. The method comprises the following steps of: first, placing a rock core saturated with homogeneous liquid into a rock core holder, and exerting confining pressure to the rock core; then injecting the homogeneous liquidinto the rock core from the inlet end of the rock core holder; measuring changing data of pressure at the inlet end of the rock core holder over time; monitoring changing data of pressure at the outlet end of the rock core holder over time; stopping the experiment when the pressure at the outlet end of the core holder changes; recording duration time during which the pressure of the homogeneous liquid from the inlet end of the core holder into the core to the outlet end of the core holder changes; and repeating the steps to obtain starting pressure gradient of the homogeneous liquid seeping inthe rock core. The method is simple and rapid, and is more in line with the technical requirements of effective utilization range estimation of oilfield blocks in low-permeability reservoirs and heavy oil reservoir development technologies, and corresponding well network optimization and oil and gas well incentive measures.

Description

technical field [0001] The invention relates to the technical field of oil and gas field development tests, in particular to an experimental method for measuring seepage initiation pressure gradient. Background technique [0002] Seepage in low-permeability porous media does not follow the traditional Darcy's law, and the relationship between seepage velocity and pressure gradient is no longer linear, but there is a "threshold pressure gradient". Oil and gas seepage in tight oil and gas reservoirs (shale oil and gas, low permeability oil and gas reservoirs), pore seepage in aquitards caused by ground subsidence caused by groundwater exploitation, and seepage in the process of cohesive soil consolidation all belong to this type of non-Darcy seepage problems. . The start-up pressure gradient of seepage in low-permeability porous media can be attributed to: ① the pores of low-permeability porous media are small, the pore surface area is large, and the interface between the roc...

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Problems solved by technology

The principles of these seepage experiment methods are usually based on the steady-state seepage model and the unsteady-state seepage model; however, the seepage experiment process takes a long time to reach a steady state, and under the current technical conditions, the data in the seepage section with low differential flow rate cannot be accurate collected, unless expensive high-precision displacement pump equipment is used; the unsteady-state experimental method needs to measure the instantaneous change of pressure in a long-term range to effectively reduce the uncertainty of the data analysis results; the capillary force in the capillary balance method cannot be measured , the experiment period is longer

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